Herpes simplex virus (HSV) infections can cause significant clinical problems and even death in individuals who are immunodeficient or suffering from disorders of skin integrity. Approximately 80% of adults in the United States are infected with HSV, 50 to 60 million of whom are infected with HSV-2. HSV-2 is the leading cause of genital ulcer disease, and genital HSV-2 infection triples the risk for sexually acquiring HIV infection. Currently, no medication can prevent primary HSV infections or decrease the incidence of recurrences. Thus, there is a huge demand for a safe and effective HSV vaccine. Using the T-RExTM (Invitrogen, CA) gene switch technology, we constructed a novel class of HSV recombinant viruses with key features of replicationdefectiveness and capability of inhibiting wild-type HSV-1 and HSV-2 infections (dominant-negative). CJ9-gD is a prototype of the dominant-negative and replication-defective HSV-1 recombinant viral vaccine that is avirulent, expresses high levels of HSV-1 major antigen glycoprotein D (gD), and cannot establish latent infection in vivo. Immunization with CJ9-gD elicits HSV-specific Ab as well as Th1-cell responses at levels comparable to those induced in wild-type HSV-1-immunized animals, and leads to full or close to full protection against HSV-1 infection in mice and guinea pigs. Considering these favorable safety and immunological profiles of CJ9-gD and aiming to maximize levels of gD2 expression, we recently constructed a dominantnegative HSV-2 recombinant vaccine, CJ2-gD2, which is more effective than CJ9-gD in protecting against wildtype HSV-2 genital infection and disease. Considering that CJ2-gD2 greatly reduces the expression of HSV-2 major envelope glycoprotein B (gB2), which like gD2, is the predominant target for both neutralizing antibody and T-cell responses, we propose to increase the immunogenicity of CJ2-gD2 by enabling it to express high levels of gB2. Moreover, given (1) that various HSV vaccines, when evaluated in humans, have either shown no clinical efficacy or failed to achieve the effectiveness demonstrated in preclinical animal models of HSV-2 infection, and (2) the documented potent immunomodulatory effect of IL-15 in stimulating Th-1 cellular immunity, the humoral immune response and in the maintenance of CD8+ and CD4+ memory T cells, we will explore whether a localized de novo IL-15 expression can augment the vaccine potential of CJ2-gD2 by constructing an IL-15/gB2-expressing CJ2-gD2. The primary goal of this research plan is to develop an optimal and cost-effective recombinant viral vaccine against HSV-2 infection in humans, which encodes three unique features: dominant-negative and replication-defective, overexpressing HSV-2 major antigens gD2 and gB2 along with expression of a broad array of other known HSV-2 antigens to achieve broad cross protection, and incorporating IL-15 to enhance the breadth and durability of the induced HSV-2-specific immune responses. The vaccine efficacy of IL15/gB2-expressing CJ2-gD2 in preventing primary and recurrent HSV-2 genital disease will be evaluated in mouse and guinea pig models of HSV-2 intravaginal infection.